This invention relates generally to telescopes and in particular to a new and novel telescope inner tube locking device and method for adjusting and then positively locking the inner tube usually known as the erector guide tube.
In a telescope of the type before mentioned, an outer tube of the telescope contains the inner erector guide tube which in turn holds the optics of the telescope and the reticle which provides a means for defining an aiming point which will be coincident with the point of impact of the bullet on the target. The reticle may take the form of a cross hair, dot and post types as well as other types.
Prior to using a rifle, handgun or shotgun in all areas for target or game shooting with a telescope attached to the firearm, adjustments are made to the position of the telescope inner erector guide tube to introduce corrections in the line of sight to compensate for windage, the distance to the target, the ballistic characteristics of a particular cartridge and to zero-in the telescope to the axis of the firearm barrel to which the telescope is attached.
These adjustments are also required due to the dimensional variations in the telescope mounts and the mechanical axis of the telescope which is rarely exactly in line with the barrel of the firearm. In addition, the trajectory of a bullet does not coincide with the line of sight which is always straight and requires test firings followed by adjustments of the inner erector guide tube that holds the optics and the reticle.
These adjustments are made in prior art devices by turning a pair of windage and elevation control screws which are spring biased with the bias spring being positioned opposite to the adjustment screws. For a more detailed discussion of the construction of the inner erector guide tube and it's placement in the outer telescope tube as well as to the adjustment screw construction, reference should generally be made to the patents cited herein and specifically to the applicant's U.S. Pat. No. 3,161,716 of D. J. Burris et al and the U.S. Pat. No. 3,222,987 of N. A. Wrigglesworth which show details on typical adjustment screw designs.
In the prior art of telescope design it is known to use various mounting configurations for holding the optics as shown in the U.S. Pat. No. 4,436,421, issued on Mar. 13, 1984 to K. Suzuki and in the U.S. Pat. No. 4,943,149, issued on Jul. 24, 1990 to E. Wahlen et al.
It is also known to provide telescopes with one adjustment screw which is spring biased by a single bias spring as shown in the U.S. Pat. No. 3,121,163, issued on Feb. 11, 1964 to G. E. Rickert and in the U.S. Pat. No. 4,986,645, issued on Jan. 22, 1991 to J. A. I. Ekstrand.
It is also known to use two adjustment screws with one bias spring which is usually a leaf spring. These configurations are shown in the U.S. Pat. No. 2,546,861, issued on Apr. 17, 1951 to L. H. Brown; in the U.S. Pat. No. 3,008,237, issued on Nov. 14, 1961 to H. N. Harris; in the U.S. Pat. No. 3,161,716, issued on Dec. 15, 1964 to D. J. Burris et al; in the U.S. Pat. No. 3,222,987, issued on Dec. 14, 1965 to N. A. Wrigglesworth; and in the U.S. Pat. No. 4,982,502, issued on Jan. 8, 1991 to A. Weyrauch.
It is also known to use two adjustment screws with two spring bias members as shown in the U.S. Pat. No. 3,642,341, issued on Feb. 15, 1972 to P. Selfried; in the U.S. Pat. No. 4,721,375, issued on Jan. 26, 1988 to H. A. M. van Dulmen; and in the U.S. Pat. No. 4,584,776, issued on Apr. 29, 1986 to D. R. Shepherd.
While the above mentioned constructions may be suitable for the purposes designed, they do not recognize the problems inherent in the use of only a bias spring acting against the adjustment screws. It has been found from experimentation over the years that once the two adjustment screws are set to a desired position by test firings of the firearm, the spring bias may not be sufficient to positively hold or lock the selected settings in place causing a misalignment and requiring more alignment test firings.
The misalignment can occur from repeated discharge of the firearm with heavy recoils that can cause misalignment of the previously set scope inner tube position. In addition, an accidental jarring or a dropping of the firearm can cause misalignment and may change the adjustment screw settings. In other words, the use of only a spring bias against the adjustment screw is sufficient during the adjustment of the screws but may not be sufficient to hold the erector guide tube in a locked position once the proper setting of the adjustment screws is obtained.
Misalignment can also occur from a backlash in the threads of the adjustment screws which is not always overcome by the bias spring acting on the adjustment screws. The applicant's novel device herein described will force this backlash out so that the misalignment can not occur.